As armies raid castles, dragons burn soldiers, and Cersei Lannister schemes away in King’s Landing, it won’t be long before everyone realizes that two most valuable resources in Game of Thrones‘ Westeros are Valyrian steel and dragonglass. Those are the only known substances that can kill White Walkers, so when the Night King and his army of the dead arrive, nothing else will matter.

Jon Snow is busy mining as much dragonglass as he can from the caves of Dragonstone, and this week’s episode re-introduced a weapon that’s worth talking a bit more about: Littlefinger’s dagger. Where have we seen that before, and why is it so important? Join me below, where we’ll also run down all of the Valyrian steel pieces we know about on the show.

A Brief History of Littlefinger’s Dagger

Back in season one, an assassin attempted to murder a comatose Bran Stark in Winterfell with this dagger, which has a dragonbone hilt. Catelyn Stark managed to stop the assassin (with an assist from Bran’s direwolf Summer), and, furious, she rode to King’s Landing to show her husband Ned Stark, who was serving as Hand of the King to Robert Baratheon at the time. There, Littlefinger dramatically reveals that he once owned the dagger, but that he lost it to Tyrion Lannister in a bet during a tourney on Joffrey’s name day: Littlefinger supposedly bet on Jaime Lannister to beat Loras Tyrell in a joust, but when Loras won, the blade went to Tyrion.

Catelyn leaves the blade with Ned in King’s Landing and heads for home, but when she captures Tyrion at the crossroads inn along the way, she inadvertently kicks off the entire War of the Five Kings. When Ned is taken captive by Cersei, Littlefinger takes the blade for his own, and we finally saw it again in last night’s episode. Baelish gives it to Bran, who subsequently passes it on to Arya, who will surely put it to good use in the Great War to Come.

But here’s the thing: for Littlefinger’s story about how he lost the knife to be true, that would mean that Tyrion needed to bet against his own brother in a joust, and that would never happen. Tyrion denies owning the dagger multiple times, and in the books, he and Jaime deduce that it was Joffrey who took the blade from Robert and hired the assassin to finish off Bran. But the whole situation is still a little murky, and some think Littlefinger hired the assassin himself so he could frame Tyrion for the crime. Maybe Bran, the new Three-Eyed Raven, can shed some light on all of this for us with a flashback or two.

All The Valyrian Steel Swords We Know About

We know Valyrian steel will be supremely important moving forward, and we also know it’s exceedingly rare. There are a few hundred scattered throughout the richest and most notable families in Westeros, but we’ve only actually seen a handful of them appear on the show. Here’s a list of all the ones we know about:

Littlefinger’s (now Arya’s) dagger

Jon Snow’s Longclaw, the ancestral sword of House Mormont, which was given to Jon by Jeor Mormont (Jorah’s father and the former Lord Commander of the Night’s Watch)

Brienne of Tarth’s Oathkeeper, one of two swords created by melting down Ned Stark’s sword Ice

Jaime Lannister’s Widow’s Wail, the other sword melted down from Ice, which was initially given to Joffrey as a gift

Heartsbane, the ancestral sword of House Tarly, which Samwell Tarly stole from his father’s home before heading to Oldtown

You can bet on all of those blades becoming hugely important as the show approaches its endgame.

Here’s one last thing to chew on: the White Walkers are technically dead, right? So if that’s the case, can Arya use her Faceless Man magic to pose as the Night King’s number two guy and suddenly slash the Night King to pieces? That’d be a hell of a way for him to go down.